Does Google still support the robots.txt noindex directive?
No, back in September 2019 Google stopped supporting the unofficial robots.txt noindex directive.
While its use should have always been a last resort, the directive is completely useless now.
What about other search engines you ask, like Bing for instance? They’ve never supported the unofficial noindex directive (opens in a new tab).
So what’s the best way to noindex pages?
The best way to noindex pages is to use the meta robots tag or X-Robots-Tag.